Noncorrosive antifreeze liquid



Patented May 30, 1933 UNITED STATES PATENT OFFICE RAYMOND J. KEPFER, 0F WILMINGTON, DELAWARE, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO E. I. DU FONT DE NEMOURS & COMPANY, OF WILMINGTON, DELAWARE,

A CORPORATION OF DELAWARE NONCORROSIVE ANTIFREEZE LIQUID No Drawing.

This invention relates to a new composition of matter having both non-corrosive and anti-freezing properties and Which is particularly adapted for use in the cooling systems of Water-cooled internal combustion engines.

It is well known that in the operation of automotive vehicles, particularly in the Winter months, it is necessary, when using those employinp Water-cooling systems, to use as a cooling medium a liquid Which Will not freeze under the conditions of operation. Various so-callcd anti-freezing liquids have been proposed for this purpose, such, for example. as ethyl alcohol, glycerol, ethylene glycol. and aqueous solutions of inorganic salts. The polyhydroxy alcohols Which are used to some extent have proven rather expensive when halts occur in the cooling systems; the employment of inorganic salts in the radiator solutions are prone to efiect undue corrosion of the various parts thereof, and While ethyl alcohol has proven to be incXpcnsivc, nevertheless when used alone, it etl ects considerable corrosion of the metal parts of the radiators in contact With it.

An object of the present invention is to provide a composition of matter which not only has a low freezing point but likewise inhibits corrosion. A further object of this invention-Iis to provide such a composition of. matter, particularly "for use in internal combustion engines, and in which the cor- 1O.--'l\'Q action of the anti-treeze liquid and the Water is inhibited. @ther objects Will hereinafter appear.

I have found that a solution containing the Water soluble lower aliphatic alcohols and principally ethanol, methanol, and propanol, in which there has been dissolved at borate which is not only soluble in the rain ticular alcohol employed but Which likewise has an appreciable solubility in Water, atfords a solution which has exceptional corrosive inhibiting qualities together With a freczin; point proportional to its alcohol content. Such a composition may be used in the cooling systems of internal combustion engines Without fear of the corrosion of the oxidizable metals such as brass, alumi- Application filed November 15, 1930. Serial No. 496,033,

num, iron, or other metals found in such apparatus by the water or acidic impurities present and with the assurance that, even though the temperature of the solution be; comes excessive, there will result substantially no corrosion of the metal surfaces.

The borates Which I have found particularly applicable for use in such compositions of matter include the alkaline earth and alkali borates which are both soluble in the particular alcohol used and, of course, in water. I have found that boran, Which is comparatively inexpensive and has these qualities, is especially suitable; While under some circumstances the organic borates, such as methyl and ethyl borate, may be employed, their use is not highly recommended as they are not readily available, have a loW vaporizing temperature, and show-no appreciable advantage over the less expensive borates. lit the organic loorates be used, they likewise, of course, should have the solubility characteristics of the preferred inorganic borates, i. e. they should be soluble in Water and in the alcohol used.

I have determined that to afford adequate protection from corrosion of metallic surfaces in contact with 764007;; or better commercial grade methanol solutions, approximately ().O5% boran is all that is usually required to render such solutions non-cor rosive. Alcohols of higher purity require less, While Wood alcohols containing appreciable amounts of pyroligneous acids or synthetic methanol which has not been entirely freed from acidic constituents may require up to 0.5% hora to insure full protection. As the concentration of the alcohol decreases a larger amount of borax is generally necessary. For example,an aqueous methanol solution containing 7 5% methanol can be rendered non-corrosive by having present approximately .1% borax While a solution containing but 15% methanol in Water should contain from 0.5 to 1% borax. lt Will be realized, therefore, When employing a concentrated or dilute methanol solution in Water an unusually small percentage of borax will render it substantially non-cor rosive.

The unexpected advantages of my composition may be shown by comparing a steel drum containing a 75:25 methanol water mixture with 0.1% borax, with another drum 5 containing an identical mixture without the borax, corrosion will generally appear in the latter drum in as short a "time as 24 hours, while the first drum will show no corrosion even after months in storage. The same freedom from corrosion, even after a o I winters driving, will be obtained 1n an automobile radiator holding an anti-freezing mixture of, say, 30% methanol, and 70% water in which approximately 0.7% borax has been dissolved.

While various aliphatic alcohols may be used in conjunction with the borax, I prefer methanol as it has several advantages over the other alcohols. As borax is but sparingly soluble even in water, particularly at low temperatures, the alcohol should preferably be a good solvent for it in order that no crystallization .occursg-and methanol is a good solvent therefor even below 0 F. Moreover, a smaller amount of methanol is required to effect the same freezing point lowering of a solution than is required for the higher molecular weight alcohols and consequently it is less expensive to use even when their cost per gallon is the same. Furagainst freezing to 20 F. will have a boiling point of 199 F. if methanol is usedand 194 F. if ethanol,-at- 10 F: the relative boiling points are 193 F. and 187 F.,.re spectively. Obviously a smaller amount of methanol will be lost by evaporation under similar operating conditions.

I have likewise found that the presence of borax in concentrated methyl alcohol solutions inhibits the corrosion of metallic surfaces in the vapor space above the solution. Whether or not this be due to the formation of methyl borate from the interaction of sodium tetraborate with methanol or due to some other cause, metal surfaces subject to the vapors from such a solution have greater protection from corrosion than similar solutions not containing a borate.

An anti-freezing non-corrosive composition for addition to the water cooling system of internal combustion engines, in accord with my invention, should contain sufiicient borax to give adequate protection from corrosion. This should be true even though the freezing point of the radiator solution is lowered only to a temperature of, say, 15 F. I have found that a concentrated methanol solution containing generally from 1 to 3% borax will give the corrosion inhibiting effect desired both in the radiator when diluted with water, and in the container prior to dilution. Due to the difficulty of dissolving the borates and particularly borax in 65 water I have found that my composition thermore, an aqueous solution protected should be prepared by first dissolving the borate in the alcohol and then adding the clear solution to the water. The amount of methanol or other aliphatic alcohol required to give the desired lowering of the freezing point will be determined, of course, by the amount thereof added to the aqueous solution. The amount of methanol required to be added to obtain protection to a certain temperature below 32 F. is approximately 1% by weight of methanol for each degree Fahrenheit.

Various changes may be made in the proportions and in the types of alcohols and borates employed, providing the alcohols be soluble in water and borates be both soluble in the alcohol and in water, without departing from this invention or sacrificing any of the advantages that may be derived therefrom.

I claim: 7

1. A process for inhibiting the corrosion of the oxidizable metals, with which the liquid and/or vaporized anti-freeze radiator composition of automobiles is in contact, which comprises contacting the anti-freeze composition containing 15% to 100% synthetic methanol with the oxidizable metals in the presence of 0.01% to 3% borax.

2. An automobile anti-freeze which is substantially non-corrosive toward the oxidizable metals of the automobile with which it contacts which comprises synthetic methanol and a borate.

3. An automobile anti-freeze which is substantially non-corrosive toward the oxidizable metals of the automobile with which it contacts which comprises 15% to 95% syn thetic methanol containing 0.01% to 3% borax dissolved therein. 7

4. A process for the prevention of the corrosive action and freezing of radiator solutions, characterized in that a synthetic methanol solution containing borax is dissolved in water to give a solution contain- 119 ing at least 15% synthetic methanol and 0.01% borax.

In testimony whereof, I afiix my signa- RAYMOND J. KEPFER. 115

ture. 

